This circuit was found in the May 1990 Radio Electronics magazine. The timings depend on the capacitors and the supply voltage depends on the relay used.
The circuit shown is from an old European publication. In it we have the way to activate a relay...
We found this circuit in a European publication from the 1990s. Transistors are still common types...
This circuit was found in an American documentation and can be added to common amplifiers of any...